Production of material libraries using sputter methods

ABSTRACT

In a process for the combinatorial production of a library of materials in the form of a two-dimensional matrix in the surface region of a planar substrate by sputtering, the planar target used for the sputtering is arranged in parallel to the planar substrate and has surface regions of different chemical composition.

The invention relates to processes for the combinatorial production of alibrary of materials in the surface region of a planar substrate bysputtering.

The parallelized production and testing of materials having suitablephysical and/or chemical properties is a sector in material researchwhich is currently greatly increasing in importance.

WO 98/47613 discloses a number of processes by which, using sputtering,CVD or PVD techniques, libraries of materials of potential interest canbe generated. Basically, this application relates to the use of suitablemasking techniques which makes possible defined deposition of at leasttwo components (which are present as separate substrates) on onesubstrate, as a result of which composite materials are obtained. Inaddition, by means of the process, by generating gradients on thesputtered substrate, complete libraries of materials of differingcomposition can be generated.

The use of numerous different masks, which need to be positioned exactlyto obtain reliable results, makes the process described complex to carryout.

It is an object of the present invention to provide a process for thecombinatorial production of a library of materials, which process avoidsthe disadvantages of the known process.

We have found that this object is achieved by a process for thecombinatorial production of a library of materials in the form of atwo-dimensional matrix in the surface region of a planar substrate bysputtering, with the planar target used for the sputtering beingarranged in parallel to the planar substrate and having surface regionsof different chemical composition (e.g. a mosaic target).

In addition, the object is achieved according to the invention by aprocess for the combinatorial production of a library of materials inthe surface region of a planar substrate by sputtering, with aribbon-shaped substrate being shifted in the longitudinal direction andat least two targets of different chemical compositions which are usedfor the sputtering being arranged over the ribbon along the direction ofshifting.

In the present invention the use of masks for generating the desiredlibraries is avoided, so that producing libraries is considerablysimplified.

The fundamental idea of the mosaic target is that a materiallyinhomogeneous target for sputtering is used for the sputtering process,with a matrix of unknown composition being first produced by thesputtering process. Not until after successful testing for the desiredphysical or chemical property is the composition analyzed of thematerials complying with the requirements. By coating the basic targetwith various other components, a gradient of the different components isproduced on the sputtered matrix during the sputtering process. Thisgradient can be useful for producing alloys of metals and/or nonmetals,mixed oxides of metals and/or nonmetals or other classes of compounds ofdifferent compositions, provided that they are accessible by means ofsputtering processes. By a suitable spatial arrangement of thecomponents on the basic target, the sputtered matrix can be divided intosectors in which, in the manner of set theory, enrichment in each caseof one of the components occurs, so that as great a range as possible ofthe potentially producible component mixtures can be generated.

Sputtering is the atomization of a solid surface by bombardment withhigh-energy ions such as O⁺ or Ar⁺ or neutral particles (FAB, fast atombeam bombardment). In sputtering, the kinetic energy of the primaryparticle, that is of the ions or neutral particles, is distributed byimpact to the atoms of the solid (target). If in this process sufficientenergy is transferred to a surface atom to overcome the surface bindingenergy, this can leave the solid as a free particle and be deposited ona substrate. In this manner, individual atoms, ions and clusters can begenerated and deposited on substrates. The kinetic energy of the ions orneutral particles is generally from 0.1 to 20 keV. Suitable sputteringprocesses are known. Since the particles released have higher energiesthan thermally vaporized particles, they can be used for depositing thinlayers on substrates, compared with what are termed PVD processes(Physical Vapor Deposition processes).

By selecting a target having surface regions of different composition,composition gradients of the material resulting on a substrate can beproduced. Gradients of this type can also be achieved according to theinvention by the material substrate being shifted spatially along anumber of targets, the targets being excited in a phase-shifted manner.

Hitherto, sputtering processes have been used to generate compositionswhich are as homogeneous as possible, and not for generating gradients,cf. Ullmanns Encyclopedia of Industrial Chemistry, 6th Edition, 1998Electronic Release, Wiley-VCH, Weinheim, Germany.

The term “library of materials” means that a multiplicity of materialsof different composition are generated on a substrate. Preferably, atleast 10, particularly preferably at least 100, different materials areformed on the substrate.

The expression “in the surface region” means that the materials areformed, for example, on a planar substrate, with the sputtered metals ornonmetals not penetrating into the substrate. This is the case, inparticular, in the case of smooth ceramic, glass, plastic, metal, orcarbon substrates. However, corresponding porous support materials canalso be used, with the sputtered metals or nonmetals penetrating atleast into the surface pores. In this case, according to the inventionthe material is formed in the topmost layer of the planar substrate,that is to say in the surface region.

The expression “planar substrate” means a substrate which extendsconsiderably further in two directions in space than in the thirddirection in space. The planar substrate need not be flat, it can, forexample, be a series of depressions or wells on or in a plate. Forexample, it can be a spot plate or a corresponding plate which hasdepressions at regular intervals. In particular, the porous supportmaterial can also be present in the form of bodies of any shape, forexample in the form of tubes which have been cut open and divided intotwo halves that can be rejoined for a subsequent catalytic test.Preference is given to porous support materials made of ceramics, metalsor activated carbons. Examples of such supports are described inDE-A-198 05 719 as auxiliary supports.

The exact configuration of the planar substrate is not restricted.Preferably, the planar substrate is subdivided into individual definedplaces which are spatially delimited from one another.

The expression “planar target” denotes a target which extendsconsiderably further in two directions in space than in the thirddirection in space. The planar target, like the planar substrate, neednot necessarily be flat. It can be provided on the surface, at least inpart, with planar metal pieces and/or nonmetal pieces of at least onemetal or nonmetal different from the target. The pieces can be fixed,for example, by glueing, soldering or welding. The spatial extension canthen be chosen during the sputtering. The planar target can be arranged,for example, horizontally and can be coated on the surface at least inpart with planar metal pieces and/or nonmetal pieces of at least onemetal or nonmetal which is different from the target. In this case thetarget is sputtered from above.

The planar target is arranged in parallel to the planar substrate. Thisensures that on the planar substrate a matrix of different materials isformed during the sputtering, since regions of different materialcompositions are present on the target. Slight deviations fromparallelity of, for example, ±5°, preferably ±2°, can be tolerated inthis case.

The target has surface regions of differing composition. In this case,at at least two different spatial positions of the target, differentsurface compositions are present.

For example, a target can be coated at different positions with foilpieces of different metal foils and/or nonmetal foils, as a result ofwhich, in a simple manner, a planar target is obtained having surfaceregions of different chemical composition.

Preferably, the target is coated with metal pieces and/or nonmetalpieces which are selected from metals of groups Ib, IIb, IIIb, IVb, Vb,VIb, VIIb and VIII, lanthanides and actinides, and also metals andnonmetals of groups Ia, IIa, IIIa, IVa, Va and VIa of the Periodic Tableof the Elements. The sputtering process can be carried out for a largerange of metals and nonmetals.

Preferably, from two to twenty, particularly preferably from two to ten,in particular from two to five, different metal pieces and/or nonmetalpieces are present on the target.

For example, the target used can be a noble metal target such as a goldtarget that is coated in a suitable manner with other noble metal foilpieces such as platinum foil pieces and palladium foil pieces. Forexample, also, an iron target can be coated in a suitable manner withfoil pieces of the elements gold, platinum and nickel. The foil piecescan be arranged on the target by chance or according to defined orderingprinciples. Preferably, foil pieces of different composition arearranged in such a manner that as many different material compositionsas possible result in different regions on the planar substrate (mosaictarget). On the planar substrate, not only are the compositionsaccording to the individual foil pieces obtained, but also mixtures oftwo or more thereof.

The sputtered matrix can also be subdivided into ordered sectors, forexample into a two-dimensional matrix, which is coated with the foilpieces according to combinatorial principles.

The sputtering parameters are selected according to the invention insuch a manner as to give an (overlapping) distribution of the differingcomponents on the substrate and thus the respective composition of thediffering samples.

The resulting layer thickness of sputtered material can vary from amonoatomic layer to about 500 μm.

The invention also relates to a process for the combinatorial productionof a library of materials in the surface region of a planar substrate bysputtering, with a ribbon-shaped substrate being shifted in thelongitudinal direction and at least two targets of differing chemicalcomposition used for the sputtering being arranged over the ribbon alongthe direction of shifting.

In this case it is a continuous process, preferably for coating ribbonsby moving the ribbon in one direction with simultaneous coating bydifferent targets by means of sputtering. Instead of a target coatedwith, for example, foils, a plurality of targets of differingcomposition are arranged over the transportable ribbon in the directionof the ribbon. The two or more targets are then excited, preferably, ina phase-shifted manner in such a manner that different materials aredeposited on the ribbon-shaped substrate in the direction of the ribbon.This can be achieved, for example, by the current intensity of theindividual targets being varied in a phase-shifted manner for theindividual components as a function of time with the ribbon running at aconstant speed. The resulting ribbon then has different compositionsover its entire length and can be tested for useful properties in theindividual sections. Suitable ribbon materials are metal ribbons, metalnets, woven metal cloths, knitted metal cloths or felted metal clothswhich can be cut into pieces for the testing for useful catalyticproperties and then analyzed. They can be processed, for example, toform tubes. The type of the ribbon material is not restricted to metals,but the carrier can, as described above, also be made up of glass,ceramics or activated carbon. Ceramics which can be used are, inparticular, oxides, nitrides and carbides as glass ceramics or sinteredquartz. Reference may be made in turn to DE-A-198 05 719.

For example, three different targets arranged one behind the other canbe excited according to a respectively shifted sawtooth function, sothat in each case only two targets act on one position of the substrateand binary mixtures with gradients are obtained.

The invention also relates to a process for the combinatorial testing oflibraries of materials which are obtained by one of the abovementionedprocesses in which individual defined places of the substrate areanalyzed for a desired property by physical and/or chemical methods andthe composition of the defined places of the substrate for which thedesired property was found is then analyzed. The analysis can also becarried out as described in DE-A-198 05 719.

The invention will be described in more detail below with reference toan example:

A round disk-shaped GeSb₂Te₄ target having a diameter of 15 cm wascoated using Co chips having a diameter of 1 cm at a distance of 5 cm.On the matrix obtained by sputtering, cobalt contents of from 1.8 to3.6% were measured. It is implied therefrom that due to inhomogeneousarrangement of such metal chip coatings on a target, inhomogeneouscoatings on a matrix are also obtained, since the inhomogeneous coatingof the target is carried over to the sputtered surface.

We claim:
 1. A process for the combinatorial production of a library ofmaterials in the form of a two-dimensional matrix in the surface regionof a planar substrate by sputtering, comprising using a sputteringtarget having a planar surface arranged in parallel to the planarsubstrate and upon which planar pieces are inhomogeneously arranged toprovide the target surface with regions of different chemicalcomposition, the pieces being of material different from that of thetarget.
 2. A process as claimed in claim 1, wherein the sputtering iscarried out using high-energy ions or neutral particles.
 3. A process asclaimed in claim 2, wherein the target is coated with pieces which areselected from metals of groups Ib, IIb, IIIb, IVb, Vb, VIb, VIIb andVIII, lanthanides and actinides, and metals and nonmetals of groups Ia,IIa, IIIa, IVa, Va and VIa of the Periodic Table of the Elements.
 4. Aprocess as claimed in claim 2, wherein the planar substrate issubdivided into individual defined places which are spatially delimitedfrom one another.
 5. A process as claimed in claim 2, wherein the planarsubstrate has at least on the surface a porous support material whichcan be present in the form of shaped bodies.
 6. A process as claimed inclaim 2, wherein the planar substrate is made up at least on the surfaceof glass, ceramics, metal and/or activated carbon.
 7. A process for thecombinatorial testing of libraries of materials which are obtained by aprocess as claimed in claim 2, in which individual defined places of thesubstrate are analyzed for a desired property by physical and/orchemical methods and then the composition of the defined places of thesubstrate for which the desired property was found is analyzed.
 8. Aprocess as claimed in claim 1, wherein the target is coated with piecesselected from metals of groups Ib, IIb, IIIb, IVb, Vb, VIb, VIIb andVIII, lanthanides and actinides, and metals and nonmetals of groups Ia,IIa, IIIa, IVa, Va and VIa of the Periodic Table of the Elements.
 9. Aprocess as claimed in claim 8, wherein the planar substrate issubdivided into individual defined places which are spatially delimitedfrom one another.
 10. A process as claimed in claim 8, wherein theplanar substrate has at least on the surface a porous support materialwhich can be present in the form of shaped bodies.
 11. A process asclaimed in claim 8, wherein the planar substrate is made up at least onthe surface of glass, ceramics, metal and/or activated carbon.
 12. Aprocess for the combinatorial testing of libraries of materials whichare obtained by a process as claimed in claim 8, in which individualdefined places of the substrate are analyzed for a desired property byphysical and/or chemical methods and then the composition of the definedplaces of the substrate for which the desired property was found isanalyzed.
 13. A process as claimed in claim 1, wherein the planarsubstrate is subdivided into individual defined places which arespatially delimited from one another.
 14. A process as claimed in claim13, wherein the planar substrate has at least on the surface a poroussupport material which can be present in the form of shaped bodies. 15.A process as claimed in claim 13, wherein the planar substrate is madeup at least on the surface of glass, ceramics, metal and/or activatedcarbon.
 16. A process for the combinatorial testing of libraries ofmaterials which are obtained by a process as claimed in claim 13, inwhich individual defined places of the substrate are analyzed for adesired property by physical and/or chemical methods and then thecomposition of the defined places of the substrate for which the desiredproperty was found is analyzed.
 17. A process as claimed in claim 1wherein the planar substrate has at least on the surface a poroussupport material which can be present in the form of shaped bodies. 18.A process as claimed in claim 17, wherein the planar substrate is madeup at least on the surface of glass, ceramics, metal and/or activatedcarbon.
 19. A process for the combinatorial testing of libraries ofmaterials which are obtained by a process as claimed in claim 17, inwhich individual defined places of the substrate are analyzed for adesired property by physical and/or chemical methods and then thecomposition of the defined places of the substrate for which the desiredproperty was found is analyzed.
 20. A process as claimed in claim 1,wherein the planar substrate is made up at least on the surface ofglass, ceramics, metal and/or activated carbon.
 21. A process for thecombinatorial testing of libraries of materials which are obtained by aprocess as claimed in claim 20, in which individual defined places ofthe substrate are analyzed for a desired property by physical and/orchemical methods and then the composition of the defined places of thesubstrate for which the desired property was found is analyzed.
 22. Aprocess for the combinatorial testing of libraries of materials whichare obtained by a process as claimed in claim 1, in which individualdefined places of the substrate are analyzed for a desired property byphysical and/or chemical methods and then the composition of the definedplaces of the substrate for which the desired property was found isanalyzed.
 23. The process of claim 1 wherein the planar pieces includemultiple planar pieces of a material different from that of the target.24. The process of claim 23, wherein the multiple planar pieces arearranged inhomogeneously on the target surface.
 25. A process for thecombinatorial production of a library of materials in the surface regionof a planar substrate by sputtering, which comprises a ribbon-shapedsubstrate being shifted in the longitudinal direction and at least twotargets of different chemical compositions which are used for thesputtering being arranged over the ribbon along the direction ofshifting.
 26. A process as claimed in claim 25, wherein the two or moretargets are excited in a phase-shifted manner in such a manner thatdifferent materials are deposited on the ribbon-shaped substrate in thedirection of the ribbon.
 27. A process as claimed in claim 26, whereinthe planar substrate is made up at least on the surface of glass,ceramics, metal and/or activated carbon.
 28. A process for thecombinatorial testing of libraries of materials which are obtained by aprocess as claimed in claim 25, in which individual defined places ofthe substrate are analyzed for a desired property by physical and/orchemical methods and then the composition of the defined places of thesubstrate for which the desired property was found is analyzed.
 29. Aprocess as claimed in claim 25, wherein the planar substrate is made upat least on the surface of glass, ceramics, metal and/or activatedcarbon.
 30. A process for the combinatorial testing of libraries ofmaterials which are obtained by a process as claimed in claim 25, inwhich individual defined places of the substrate are analyzed for adesired property by physical and/or chemical methods and then thecomposition of the defined places of the substrate for which the desiredproperty was found is analyzed.